3-NRG-03
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Contents
Outcomes
- Pupils understand that work done is energy transferred.
- Pupils understand that power is the rate of doing work.
- Pupils can perform simple calculations of work done and power developed.
Specification References
- 4.9, 4.10, 4.13, 4.14
Main Body of Lesson
- Remind pupils of their previous work on energy transfers and the conservation of energy.
- Explain that transferring energy from one form to another is the process of doing work.
- State formula for calculating work done = force × distance.
- Pupils calculate the work done dragging a wooden block across their benchtop.
- Introduce equation for calculating (change in) gravitational potential energy as a form of the work done equation.
- Give pupils examples where the same amount of work is done in different amounts of time (e.g. riding a bike up the same hill quickly and slowly).
- Introduce the concept of power as the rate of doing work (i.e. power = work done / time taken). A more powerful device is able to convert energy from one form to another quicker than a less powerful device.
- Pupils calculate the power they developed in the previous running-up-and-down-the-stairs task.
Practicals/Demonstrations
- Pupils use newtonmeters to calculate work done (against friction) as they drag a wooden block across the benchtop.
- Pupils calculate the work done and the average power developed as they (repeatedly) climb a set of stairs.
Plenary
- Pupils sort a range of household devices (e.g. television, washing machine, power shower, oven, iPod, etc) into order of power consumption (slide available).
Homework
Additional Information
Resources Required
- Newtonmeters
- Wooden blocks with hooks
Safety/Hazards
- Overstretched newtonmeters can be hazardous.